1 /*
2 * Copyright (c) 2021 Huawei Device Co., Ltd.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15
16 #include "base/geometry/quaternion.h"
17
18 namespace OHOS::Ace {
19 namespace {
20
21 constexpr double KEPSILON = 1e-5;
22
23 } // namespace
24
Slerp(const Quaternion & to,double t) const25 Quaternion Quaternion::Slerp(const Quaternion& to, double t) const
26 {
27 if (t < 0.0 || t > 1.0) {
28 // https://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/slerp/index.htm
29 // a scalar between 0.0 (at from) and 1.0 (at to)
30 return *this;
31 }
32
33 Quaternion from = *this;
34
35 double cosHalfAngle = from.x_ * to.x_ + from.y_ * to.y_ + from.z_ * to.z_ + from.w_ * to.w_;
36 if (cosHalfAngle < 0.0) {
37 // Since the half angle is > 90 degrees, the full rotation angle would
38 // exceed 180 degrees. The quaternions (x, y, z, w) and (-x, -y, -z, -w)
39 // represent the same rotation. Flipping the orientation of either
40 // quaternion ensures that the half angle is less than 90 and that we are
41 // taking the shortest path.
42 from = from.flip();
43 cosHalfAngle = -cosHalfAngle;
44 }
45
46 // Ensure that acos is well behaved at the boundary.
47 if (cosHalfAngle > 1.0) {
48 cosHalfAngle = 1.0;
49 }
50
51 double sinHalfAngle = std::sqrt(1.0 - cosHalfAngle * cosHalfAngle);
52 if (sinHalfAngle < KEPSILON) {
53 // Quaternions share common axis and angle.
54 return *this;
55 }
56
57 double half_angle = std::acos(cosHalfAngle);
58
59 double scaleA = std::sin((1.0 - t) * half_angle) / sinHalfAngle;
60 double scaleB = std::sin(t * half_angle) / sinHalfAngle;
61
62 return (scaleA * from) + (scaleB * to);
63 }
64
65 } // namespace OHOS::Ace
66